1. Field of the Invention
This invention relates generally to the manufacture of sliders for slide fasteners, and more particularly to a method of making an injection-molded slide fastener slider in which a slider body and a pull tab are molded on a single mold in a coupled or assembled state.
2. Prior Art
In the manufacture of slide fastener sliders, it has been customary practice to first form a slider body, an arch-shaped support lug and a pull tab independently of each other by injection-molding, and then assemble these three component parts into a slide fastener by ultrasonically welding the support lug to an upper wing of the slider body with the pull tab pivotally connected with the support lug. The conventional practice has a drawback however that the ultrasonic welding provides various degrees of bonding and involves an incidental welding failure which cannot be detected by visual inspection, lowering the rate of production.
With the foregoing drawback in view, a somewhat successful method has been proposed by U.S. Pat. No. 2,509,278 in which a slider body and a pull tab are molded simultaneously in only one molding step in a coupled or assembled state. The proposed method employs a mold composed of two mold members or halves constructed to form the front and rear portions of a slider body, respectively. For connection with the slider body, the pull tab is molded in a tilted position in which the pull tab extends obliquely to an upper wing of the slider body at an angle of 45 degrees. The mold further includes two opposed slide cores movable sidewise into the mold halves so as to form simultaneously an aperture in the pull tab in which a support lug is to be threaded, a transverse hole in the support lug, a spindle or pintle received in the transverse hole, and a gap between the pintle and the upper wing.
The method disclosed in the above-identified U.S. patent is advantageous in that the slider body and the pull tab can be molded simultaneously in a single molding step in a coupled state. This method however is still unsatisfactory in that the slide cores are complicated in shape and configuration and hence need to be finished on a high precision machine. The mold having such complicated slide cores can produce only a small number of molded sliders per mold, resulting in expensive products. The use of such complicated mold involves a large amount of objectionable burrs formed on a molded slider and hence is not suitable for mass-production.